A winter outbreak of acute histoplasmosis in northern Michigan.

In January 1980, an outbreak of 138 cases of acute pulmonary disease occurred among employees of a Michigan limestone quarry. The source of exposure was a vessel repair building (relative risk = 5.8) and the time of exposure was January 10 (relative risk = 2.4). Work activities associated with the specific place and time suggested exposure to a pulley which had been stored in a ring-billed gull nesting area as the cause of illness. Histoplasma capsulatum was recovered from the nesting area, the pulley, and the sputum of several patients. Early serologic testing confirmed the diagnosis of acute pulmonary histoplasmosis.